I wrote a while back about how my desktop screens now had areas that were 'good' and 'bad' for me, and mentioned that I had recently noticed this, calling it a story for another time. That time is now. What made me really notice this issue with my screens and where I had put some things on them was our central mail server (temporarily) stopping handling email because its load was absurdly high.

In theory I should have noticed this issue before a co-worker rebooted the mail server, because for a long time I've had an xload window from the mail server (among other machines, I have four xloads). Partly I did this so I could keep an eye on these machines and partly it's to help keep alive the shared SSH connection I also use for keeping an xrun on the mail server.

(In the past I had problems with my xrun SSH connections seeming to spontaneously close if they just sat there idle because, for example, my screen was locked. Keeping an xload running seemed to work around that; I assumed it was because xload keeps updating things even with the screen locked and so forced a certain amount of X-level traffic over the shared SSH connection.)

When the mail server's load went through the roof, I should have noticed that the xload for it had turned solid green (which is how xload looks under high load). However, I had placed the mail server's xload way off on the right side of my office dual screens, which put it outside my normal field of attention. As a result, I never noticed the solid green xload that would have warned me of the problem.

(This isn't where the xload was back on my 2011 era desktop, but at some point since then I moved it and some other xloads over to the right.)

In the aftermath of the incident, I relocated all of those xloads to a more central location, and also made my new Prometheus alert status monitor appear more or less centrally, where I'll definitely notice it.

(Some day I may do a major rethink about my entire screen layout, but most of the time that feels like yak shaving that I'd rather not touch until I have to, for example because I've been forced to switch to Wayland and an entirely different window manager.)

Sidebar: Why xload turns green under high load

Xload draws a horizontal tick line for every integer load average it needs to display the maximum load that fits in its moving histogram. If the highest load average is 1.5, there will be one tick; if the highest load average is 10.2, there will be ten. Ticks are normally drawn in green. This means that as the load average climbs, xload draws more and more ticks, and after a certain point the entire xload display is just solid green from all of the tick lines.

This has the drawback that you don't know the shape of the load average (all you know is that at some point it got quite high), but the advantage that it's quite visually distinctive and you know you have a problem.